1. Field of the Invention
This invention relates to slide fastener elements, which is made of a helically wound synthetic resin monofilament and which has basically interengaging heads and turns, and relates to the method of forming the above mentioned slide fastener elements.
2. Prior Art
In prior art, for example, in U.S. Pat. No. 3,057,030, as shown in FIG. 18, slide fastener elements made of a helically wound synthetic resin monofilament are formed by pressing a monofilament at suitable intervals in order to form widened portions. Then, this pressed monofilament is wound helically, while the widened portions are used as bending portions to be interengaging heads A and turns B.
However, in these slide fastener elements, the interengaging heads A and turns B of the slide fastener elements are formed by pressing the monofilament from the both upper and lower sides, further, they are provided in planes perpendicular to fastener tapes of a slide fastener chain respectively at the bending portions. Therefore, during the slide fastener chain is formed or used, the bending portions are often disarranged from their precise locations and the cross section of the slide fastener elements is often deformed. As a result, the slide fastener elements can not keep precise interengagement surely.